If any of you have seen all of the remastered Green Hill, you can expect something different from the remastered stages, Green Hill was supposed to be the tamest remaster, so don't expect the other levels to be less unique.

So far I can't find any other sources on this, but it looks like Mania's version of Green Hill will be as long as the original first two Green Hill acts combined. I'm glad the stage is so expansive, and I'm sure that this map made from gameplay screenshots doesn't even tell the full story!

I think Tails had two different running animations in Sonic 3 (and probably Sonic 2) anyway; one where his tails could be seen actually moving, and one where his tails were whizzing so fast they looked more like the wheel thing you see when flying/running as Tails in SRB2 currently. Wouldn't be surprised if it's the same in Mania, but I could be wrong of course.

Mania has three running animations. Knuckles's legs are spirals just like Sonic's in his fastest state, and Tails's is exactly like the wheel that Monster Iestyn described. In the video, she said there are two giant rings for special stages hidden in each act (akin to S3&K), and that Sonic's Dropdash is proportional to his momentum; If he's standing still, the dropdash won't be that fast, but if he's running it will be closer to a fully charged spindash.